With the ongoing use of threaded fittings in industrial applications, internal and external threads are continuously formed to threadingly secure fittings. A number of tools are available for forming threads. For tubular fittings, a tool, such as tool 10 as depicted in FIG. 1, forms internal threads within walls of a cavity. Tool 10 is an elongated member having threads 12 formed thereon to cut or mill internal threads upon the walls (not shown) of a cavity. Thus, the internal threads may be formed and may extend along the walls of the cavity.
However, in the prior art, the axial depth along which the internal threads may extend is dependent upon the dimensions of the tool and the obstructions it may encounter. As shown in FIG. 1, tool 10 is an elongated member having a closed end 14 which enters the cavity to form internal threads upon walls of the cavity. The internal threads may extend as far as tool 10 can be inserted through the cavity. In many situations regarding tubular fittings, for example, in an anti-lock brake valve, the cavity of a female fitting has a floor around an axially disposed protuberance having a top extending upwardly from the floor, which interferes with the closed end of conventional tools.
In use, a male tubular fitting, which threadily inserts into the female tubular fitting, typically has an open end that receives the protuberance and engages with the cavity floor. When manufacturing the female fitting, the protuberance obstructs the closed end 14 of tool 10 and, in turn, limits the depth down to which internal threads may be formed and extend along the cavity walls. As a result, no internal threads may be formed past the top of the protuberance to the surface adjacent the cavity floor. Thus, a male tubular fitting is prevented from threadily attaching past the top of the protuberance of the female fitting. This tends to affect sealing integrity and allow unwanted leakage.
Although the existing cutting and milling tools may suffice in securing tubular fittings, the obstruction as described above creates an undesirable limitation which calls for an improvement to the existing tools. The absence of threads formed past the top of the protuberance to the internal surface adjacent floor of the cavity sacrifices strength in the attachment of the tubular fittings. That is, having internal threads formed past the top of the protuberance increases the strength in holding the tubular fittings together during normal environmental use, for example, in an antilock brake valve, in which the tubes engage a flared cone fitting.
Therefore, what is needed is a threading tool which forms internal threads upon cavity walls having a floor around an axially disposed protuberance having a top, wherein the internal threads extend along the walls past the top of the protuberance to the surface adjacent the floor.